applying mirror then resetting loc and rot does not set mirror properly
First apply rotation and scale (scale is not need here but it is better for the future) :


Ctrl+A then choose 'rotation &amp; scale'





Now set the 3D cursor at the center of the 3D space (as the picture is centered also) : Shift+S, then cursor to center
Then place the object to the center : Shift+S, then selection to cursor 
Go to edit mode and replace the eye


The left part (her right) is a bit offset... but no human face is totally symetrical...